RESUMO
Melanins are implicated in the pathogenesis of several human diseases, including some microbial infections. In this study, we analyzed whether the conidia and the yeasts of the thermally dimorphic fungal pathogen Paracoccidioides brasiliensis produce melanin or melanin-like compounds in vitro and during infection. Growth of P. brasiliensis mycelia on water agar alone produced pigmented conidia, and growth of yeasts in minimal medium with L-3,4-dihydroxyphenylalanine (L-DOPA) produced pigmented cells. Digestion of the pigmented conidia and yeasts with proteolytic enzymes, denaturant, and hot concentrated acid yielded dark particles that were the same size and shape as their propagules. Immuofluorescence analysis demonstrated reactivity of a melanin-binding monoclonal antibody (MAb) with the pigmented conidia, yeasts, and particles. Electron spin resonance spectroscopy identified the yeast-derived particles produced in vitro when P. brasiliensis was grown in L-DOPA medium as a melanin-like compound. Nonreducing polyacrylamide gel electrophoresis of cytoplasmic yeast extract revealed a protein that catalyzed melanin synthesis from l-DOPA. The melanin binding MAb reacted with yeast cells in tissue from mice infected with P. brasiliensis. Finally digestion of infected tissue liberated particles reactive to the melanin binding MAb that had the typical morphology of P. brasiliensis yeasts. These data strongly suggest that P. brasiliensis propagules, both conidia and yeast cell, can produce melanin or melanin-like compounds in vitro and in vivo. Based on what is known about the function of melanin in the virulence of other fungi, this pigmented may play a role in the pathogenesis of paracoccidioidomycosis
Assuntos
Humanos , Paracoccidioides/fisiologia , Paracoccidioides/genética , Paracoccidioides/imunologia , Paracoccidioides/virologia , Pigmentação da Pele/fisiologia , Pigmentação da Pele/genéticaRESUMO
O presente estudo trata dos resultados obtidos, do ponto de vista micologico e imunoquimico, de duas amostras de Paracoccidioides consideradas como pertencentes a espécie cerebriformis, criada por MOORE em 1935 e mantidas desde aquela época, através de repiques em agar-Sabouraud, na Micoteca do Instituto de Medicina Tropical de Säo Paulo. Após cerca de 60 anos, tais amostras conservavam as mesmas características descritas por MOORE (1935). Näo foram registradas lesöes experimentais em cobaias inoculadas por via intratesticular, näo se demonstrando também, pelas técnicas SDS PAGE e Western blotting...